Effects of C‐N ratio on growth, survival and proximate composition of Macrobrachium rosenbergii post larvae reared under a corn starch based zero‐exchange brackish water biofloc system

Abstract

A 3-week nursery phase for giant river prawn, Macrobrachium rosenbergii post larval (PL), was conducted in biofloc systems at increasing carbon-nitrogen (C-N) ratios of 10:1 (C-N10), 15:1 (C-N15), 20:1 (C-N-20) and 25:1 (C-N25) versus a clear water system (40% water exchange every 2 days and no additional carbon). A total 400 PLs (15.90 ± 1.29 mg) were cultured in tanks (100 L) filled with brackish water (12‰), and corn starch was the carbon source. Growth, survival, feed conversion ratio (FCR), whole body proximate composition, water quality parameters, biofloc volume, zooplankton and proximate composition were measured. Total ammonia nitrogen (TAN) and nitrite nitrogen (NO 2 -N) were significantly lower in all biofloc systems as well as containing increased zooplankton groups (ciliates, rotifers and nematodes). Specific growth rate (SGR) was similar between the control (9.29 ± 0.35% day −1 ) and the CN-20 (9.47 ± 0.18% day −1 ) and CN-25 (9.34 ± 0.20% day −1 ) treatments; however, SGR significantly declined in the C-N10 treatment (8.03 ± 0.10% day −1 ). Survival was unaffected by treatments while a higher survival (87.34%) was in CN-20 and it was followed by CN-25 (80.34%), control (80.33%), CN-10 (77.0%) and CN-15 (76.66%) respectively.The best FCR was in the C-N20 treatment at 2.65, but was not statistically different than the control at 3.12. However, crude protein of the PLs was significantly higher in the C-N15, C-N20 and C-N25 treatments compared with the control. The present findings indicate that the water quality was better managed in the biofloc treatments compared with the control; however, lower C-N ratios of 10 and 15 can negatively impact prawn growth compared with the control or higher C-N ratios of 20 or 25.

Effect of C/N Ratio Levels and Stocking Density of Catla Spawn (Gibelion catla) on Water Quality, Growth Performance, and Biofloc Nutritional Composition in an Indoor Biofloc System

“…Although there was no signifcant diference in TAN-N concentration in diferent stocking densities, a higher mean concentration of nitrogenous compounds in a higher stocking density could be the result of higher biomass in the system and retarded development of nitrifying bacteria before biofoc formation [50,54,55]. Te presence of more nitrifying bacteria converts ammonia to nitrite and then nitrite to nitrate which might have resulted in increased nitrate-N concentration at a higher stocking density in BFT [28,56]. Becerril-Cortés et al [57] recorded similar nitrate-N concentration for tilapia fry.…”

“…In zero water exchange tanks, TSS tends to increase over time primarily due to decreased water exchange, a high amount of organic substances, and an increase in microbial biomass [58]. Excessive TSS levels can become detrimental, particularly with some fsh; however, the ideal TSS concentration for fsh in biofoc is not determined [56,59]. Te TSS concentration up to 300 mg/L showed no negative efect on growth performance of goldfsh larvae [8].…”

“…Te increase in the C/N ratio and stocking density increased TSS and foc volumes which might have reduced the survival of spawn at a higher stocking density. Hosain et al [56] observed lower survival of Macrobranchium rosenbergii postlarvae at a higher foc volume of up to 10 ml/L when molasses and wheat bran were used as a carbon source. Similarly, in the present study, foc volume increased over time, which might have led to reduced survival of catla spawn at higher stocking densities.…”

“…Survival is considered the most important parameter for culturing success during the larval and nursery phases. Higher survival at C/N 20 compared to a lower C/N ratio could be due to better water quality and greater availability of prey in the BFT system [8,56,73]. Te consumption of microbial foc enhances larvae tolerance to environmental stress, hence, improving survival [73,74].…”

Whiteleg shrimp Litopenaeus vennamei: Current status, future prospects and opportunities for Bangladesh Aquaculture

“…Moreover, there are additional benefits to the animal including better growth and feeding efficiencies as well as immunity and disease resistance (Ahmad et al, 2017;Panigrahi et al, 2018;. Biofloc contains proteins, lipids, minerals, vitamins, amino acids, and fatty acids as well as enzymes, immunostimulants and natural probiotics (Ahmad et al, 2017;Hosain et al, 2021c). Now, Litopeneaus vannamei BFT based system are being practiced in fresh, brackish and marine water environments (Table 5).…”